1. Field of the Invention
This invention relates to a member for recording information. More particularly, it relates to a recording member which exploits the removal by vaporization, the deformation, etc. of a recording thin film formed on a substrate as effected with heat from a recording beam such as laser beam or with heat generated indirectly through auxiliary means.
2. Description of the Prior Art
A method of recording information onto a disk and playing them back therefrom by the use of light is stated in, for example, a literature "A Review of the MCA Disco-Vision System" presented by Kent Broadbent in the 15th SMPTE Technical Conference & Equipment Exhibit. Hereunder, the principle will be briefly explained.
FIG. 1 is a diagram which illustrates the principle of the method of recording information on a predetermined medium, for example, a disk by the use of light. The disk is such that a thin film for recording 2 is deposited on the surface of a transparent circular substrate 1 which is made of glass, a synthetic resin or the like. It is rotated at high speed with a shaft 3 used as a rotary shaft. Under the state under which a lens 4 is brought close up to a predetermined distance from the disk 1, a laser beam 5 which is modulated into the form of pulses in correspondence with information to-be-recorded (not only the laser, but also an electron beam etc. can be employed as the beam) is focused and projected onto the recording thin film 2. Thus, those parts of the recording film 2 on which the laser beam 5 has been projected are heated by the laser beam and are fused and deformed or vaporized off. As a result, the shapes, sizes and positions of apertures or recesses which are formed in the recording thin film 2 and which have minor diameters of approximately 0.5 .mu.m-1.2 .mu.m correspond to the information applied through the laser beam. That is, the information such as pictures and voices are recorded in the recording thin film 2 in the form of the apertures or recesses. The recorded information can be played back in such a way that, while rotating the disk 1 at high speed similarly to the above, a laser beam is condensed and projected onto the recording thin film of the disk 1 in which the information have been recorded, so as to detect e.g. the intensities of reflected light. Heretofore, recording materials of good recording characteristics have been investigated. Any of the recording materials hitherto proposed, however, has been unsatisfactory in points of the quality of a recorded picture, etc.
In addition to the method as above stated wherein the laser beam or the like is used as the recording beam and the information are recorded by exploiting the vaporization or the fusion and deformation of the recording member, there is a method as stated below. In this method, a thin film whose threshold voltage for electrical switching lowers upon projection of light is held between electrodes on both sides. The thin film is illuminated with a voltage applied thereto, and thus causes the switching in the illuminated part. Parts of the electrodes adjoining the switched part are perforated by heat generated by the switching. Thus, an information is recorded. Except the property of being electrically conductive, properties which are required of the material of the electrode serving also as the recording member in this case are substantially the same as those which are required of the recording member in the foregoing case of the direct recording resorting to the heat of the laser beam projection. Accordingly, a recording member which is electrically conductive can be employed for both the methods.
The following references are cited to show the state of the prior art:
Japanese Patent Application Publication No. 40479/1971;
U.S. Patent Application Ser. No. 829,892 now U.S. Pat. No. 4,238,803;
Japanese Patent Application Laying-open No. 17144/1974.